Refractory lined furnaces have been used for many years to melt glass. Many standard refractories, however, have a tendency to become slowly dissolved or corroded by the glass until the furnace begins to leak. As a result, providing a protective liner for the furnace has been proposed. In these lined furnaces, the liner generally is formed of a corrosion resistant material.
Molybdenum, platinum, platinum alloys, and, to some extent, steel alloys and iron have long been recognized as materials having a higher resistance to wear than conventional refractory and are considered useful in the construction of glass melting furnaces. Molybdenum, for example, has been used an an electrode material and as a lining where high glass velocities produce rather severe corrosion.
Joule-effect heating is a preferred method of melting glass in a furnace of the type described herein.
U.S. Pat. No. 4,366,571 issued to Ronald W. Palmquist on Dec. 28, 1982, discloses a typical electric furnace construction employing the use of a molybdenum liner. In the Palmquist patent, the space between the liner and the refractory wall is narrow, and thus convection currents caused by the heat in the furnace are eliminated or substantially reduced within such space thereby materially reducing convection corrosion of the refractory. The space acts as a trap for a mixture of corrosion products and thermoplastic material. Since corrosion products confined in the space are not continually swept away, corrosion of the refractory is inhibited.
Also, passive cooling is suggested to seal the space and prevent the circulation of the material retained therein. If desired, one or more cooling pipes may be provided to carry cooling gas near end portions or margins of liner. The resultant extra cooling usually assures a seal by virtue of frozen glass adjacent the ends of the liner space.
All of these suggestions are aimed at reducing the rate of corrosion in the space between the liner and the refractory wall. I have developed a method which uses a refractory-type material to benefit the process of producing molten material.